1. Field of the Invention
The present invention relates to a facsimile system and, more specifically, to a system for interfacing between facsimile machines and facsimile telephone lines.
2. Description of the Related Art
Facsimile transmission of documents over electronic transmission lines has become increasingly prevalent in recent years. The attractiveness of facsimile transmission stems principally from its nearly instantaneous speed, as compared to at least a day or more for the physical delivery of documentary material.
With the expanded usage of facsimile, it has become commonplace for the sender of a facsimile transmission to receive a busy signal from the dialed facsimile telephone number, indicating that the facsimile machine at the other end is either sending or receiving another document, and is at least momentarily unavailable. Such a result partially defeats the advantage of instantaneous transmission.
To combat the problem of having a constantly "busy" facsimile line, many companies now have more than one facsimile telephone number. Such multiple independent line systems, however, are disadvantageous in that the sender must attempt to obtain a connection with each line until a free line is found. Such attempts waste time and often result in unnecessary telephone toll charges.
Another disadvantage of prior art multi-line systems is that they require the purchase and operation of a corresponding number of expensive facsimile machines. Thus, it has been impossible to date for a company with only one facsimile machine to both send and transmit messages simultaneously, although situations often arise in which such action would be desirable.
In order to help free up "busy" transmission lines, facsimile machines have been developed which contain an internal memory for storing a number of incoming and outgoing facsimile messages. With this type of machine, an outgoing message can be inputted, stored, and transmitted later during a "non-peak" period that evening. The storage of incoming messages is also desirable in that a temporary "out of paper" condition of the facsimile machine printer will not prevent messages from being received, and will thus avoid a backup of incoming calls. While this enhanced type of facsimile machine with memory is convenient and versatile, it is still limited in that only one facsimile message can be received or transmitted at a time. Accordingly, if more than one party wishes to transmit or receive on the facsimile telephone line at a particular moment, the line may still be busy.